This research program aims at understanding the regulation of viral and cellular functions which are responsible for the altered phenotype of cells transformed by oncogenic viruses, and also at understanding some basic parameters of gene induction and expression which may differentiate transformed from normal cells. The project consists of seven parts, listed below: 1. The study of the functions regulating the integration of the viral genome into the host DNA in polyoma transformed cells, and the effects of integration on viral gene expression. 2. The study of the 48K host tumor antigen which is induced in cells transformed by oncogenic viruses, and its role in the expression of the transformed phenotype. 3. The investigation of the primary viral functions controlling the phenotype of SV40 transformed cells, and of the permanent or transient requirement of such functions for the expression of transformation. 4. The study of the expression of specific Herpes virus genes after integration into cellular DNA, and the relevance of such genes to transformation. 5. The study of the mechanism of induction of plasminogen activator in normal cells by a diffusible factor produced by transformed cells. 6. The study of the importance of cellular and endogenous viral genes in determining susceptibility to radiation leukemia. 7. The investigation of the role of RNA-Helix destabilizing proteins in the regulation of eukaryotic translation.